1. Field of the Invention
This invention relates to a parallel-moving apparatus for use in a positioning apparatus used in various measuring apparatuses, precision machine tools and semiconductor exposing apparatuses etc., and a lens moving device in an exposing apparatus using the same.
2. Related Background Art
In various measuring apparatuses, precision machine tools and semiconductor exposing apparatuses etc., it is necessary to effect the positioning of an object to be measured, a workpiece or a lens highly accurately. Particularly for movement of a holding table supporting the object to be measured thereon in a vertical direction or the positioning of the lens in the direction of the optical axis thereof, it is required to control minute displacement highly accurately. For this purpose, there has been developed a parallel-moving apparatus capable of converting large displacement into minute displacement.
FIG. 5 of the accompanying drawings shows an example of the parallel-moving apparatus according to the conventional art (Japanese Patent Publication No. 57-35799), wherein a movable table 51 is moved up and down by three sets of displacement reducing mechanisms 54a, 54b, 54c provided on a fixed table 52. The displacement reducing mechanisms 54a, 54b, 54c, each comprise wedge-shaped driving members 54d, 54e, 54f provided between the fixed table 52 and the movable table 51, first needle-like roller trains 56a, 56b, 56c provided between the wedge-shaped driving members and the fixed table 52, and second needle-like roller trains 56d, 56e, 56f provided between support plates 51a, 51b, 51c secured to the movable table 51 and the wedge-shaped driving members 54d, 54e, 54f. The wedge-shaped driving members 54d, 54e, 54f of the three sets of displacement reducing mechanisms 54a, 54b54c are integrally coupled together by a connecting plate 54g, and are moved along the surface of the fixed table 52 by the push rod 55a of a micrometer head 55 urged against one end surface of the fixed table 52. That is, when the micrometer head 55 is driven, the three wedge-shaped driving members 54d, 54e, 54f, are each horizontally moved by an equal distance at a time, whereby the movable table 51 is moved up and down while maintaining its parallelism to the fixed table 52. The relation that .delta.Z=.delta.X.tan(.theta.) is established among the angle of inclination .theta. of each wedge-shaped driving member 54d, 54e, 54f, the amount of horizontal movement .delta.X thereof and the amount of vertical movement .delta.Z of the movable table 51. Therefore, the smaller the angle of inclination is of the wedge-shaped driving members 54d, 54e, 54f, the easier it becomes to control the amount of vertical movement of the movable table 51 highly accurately.
Also, there has been developed an exposing apparatus in which a parallel-moving apparatus is incorporated into a lens-barrel to correct the magnification of a projection lens (see Japanese Patent Publication No. 60-171157).